Method of separating uranium from alloys



U ite. States Patent it LuSuanY.itQkiflbDut%4T -1Qm' toxfumaccecoolbelow the melting temperature of the thorium-magnestummutechc $942968(5896') led V tth bl h h han a L p :contento ecruci e, w ic YWas WTHODatsolidpieceof metal contahfing'modistincnphases was machinedolf .in .alathe, {and the centrakportion of each phase was removed and :Jcleaned.,Samples :of .both assignorstothe United States of Americaastrepresented phases were zanalyzed, for u anium .by ten ammonium bytheiUnitedStates Atomic EnergyCummission thiocyanatespectrophotometricmethod gandforuthorium t r i, gravimetricallyzby. oxalate preoipitation.TIPhewresults-of No Drawing Flled 1957 696389 these determinaticnstatvarious temperatures .=are comltremotChiotti "and Howard E. Shoemaker,Ames, Iowa,

10 Claims. 7 (Cl. 75-84. 1) piled in Table I.

Table Thisdnvention deals with therecovery of 15 mmmummssolved,

from metallicuranium-thorium mixtures part cua 'tliereentxlotilne larfrom tor'alloys containing the in 9 t t t t comparatively small amounts.Mar-3% Mz:1 5% ure-Ms A number of, reactors, the. so-called breederreactors, f use tho ium as breeding material, often in the .fqrmeof ablanket arranged aroundhthe fissicnable-fuelmaterial. 5 "55 "Thebreeding material captures and reacts withneutrons 110 t 80 not capturedby the fissionablemateiial and form siUz 'd, 160 $33 a fissionableuranium isotope, by n, 7 reaction and sub- 2:3 Egg Egg sequent fl-decay.Such, reactors -using (thorium as blanlr 61 550 etmaterialaredescribed,for instance, in application 1 558 1 18 Seria1No.'72l-,10 8' on -Fast Neutron ReactionSystern, 11 ,2' 1:450 filed byw'alter H. Zinn on'Jannary -9,"l-947. 1 5 4 3 131670 1 Operationofwthese reactors is usually F discontinued at a point when the U-content is's below :1 percent :by 30 .Wei'ghttofthe-,neutron-reactedthorium mass. (Through ounthe app i ation per entages :given are percentby weight.) tQneaccount of this srnall-ratio-yof-Um -it-:is mill td ifil l Y S 1 l an r ve t i ur ium LS whentahout 6'5 percentrma gnesiumwerestadded toi the tope. Aqueous methods using a solubn-p f ;th ;-imadi ftholqium inass ljshowfidianiaverage mhariumi:conitefitfibf ratedmetal have been used heretofore for this p p 0.91-3 percent, the contentbeing somewhat lower when but these methods have the disadvantage thatthe uranithe h i content was 1 i th magnesium-rich um compounds obtainedfromqtheseraqueous solutions phase, The balance of m uranium.rih phasewas have to be converted to the metal for most reactors in fi u i Used-1 ""ltwas also found that two liquid phases can be ob-EI'E'FYiSHaEIObleQFQf llihis illzlflMQ E i ifi p fi tained at atemperature lower than the melting point of Separating i m f l t. thereof u anium by incorporating a further component, name- .W i 9 uranium isan dirwtlr a e-me '19 hnnmn, into the alloy. The quantity of thechroiQlT R- mium should be high enough to form the uranium-chro-"Ibis/315 p l this invention to PI :P 45 mium eutectic, which contains5.2 percent of chromiess 'of-recovering-uraniumfrom"thorium-uraniumimixi h ll f th iu present, B adding this tures,0Y$ui 1h gl y QIA ZQJ J M a, "f amounti of chromium, the temperature atwhich two liqare obtained is reduced to about 860 (3., as ared with 1132C. for pure uranium. The addiabout 5 percent of chromium, based on thetotal um content present in the alloy or metallic mixture, p theformation of a uranium-rich liquid phase These' data showthat-theseparation'of' uranium from thorium :is" better :withlincreasingmagnesium content and with decreasing temperature. V

The turan'iumnich Iphase's formed in these experiments,

It was 'found t-hat uranium is very little solubleminitail m-r chnmanaiu ahmiu all and e e less soluble in puremagnesium. It was alsoToundthat; .Q011l7 7 versely, he aa s nl t leht b e i Thevarious=solubilities or uranium in pure magnesium! v ries and inthreemagnesiumghprium alloysmgntaining {5535 con ng from 0.2 to 0.6 percentof thorium when and 16 percent' of ithorium, respectively, were ldeterff eq brated with a magnesium-thorium alloy containing mined. Inthesetests uranium Was.. ,jalways present-in m j Sarto percent ofmagnesium. While the addin' xc amount in order to make sure that themagi tion' of chromium has the great advantage of a lower sium-ri ehphases were saturated in uranium. Narious-de-:""separation temperature,it has the disadvantage of revices were used for this purpose, onebeing, for instance, iring;; an additional step, namely, that ofuraniumla lel m c uc bl int whic thol ompqnc ts were 7, omium separationif chromium-free uranium is deintroduced and held tunder an atmosphereEof argonifgas. -fillislret l. separation can be carried out by anyproc- The, crucible sealed, by,-we1ding, and thersealed crug lcnown inthe art; it does not form part of this invencible wast enclosed in awelded jacket of stainlessnsteel; T ttion; the assemblynwasvithen heatedin an oscillating resist: V, "Ihe process of this invention for theseparation of ance f n nace rotated back and fonth through urnilllflgflom thorium contained in a metallic mass (the an are of'about180 C. once about every 50 S QQQdS-I 5 ,te Ieniass is to comprisemetallic mixtures and alloys) For solubility ndeterrninations, up t 0; 800 ,Q, rotation t thus'comprises adding magnesium to the mass in aquanwas carried out-for '2 hours, whiletor those attemperaijjjjfltyntoeflobtain a content of from 48 to percent by lures i800 Mi 1.21 9 .C- l lgi'ettlll sztim iiwxe le-t v.uieit-llitin themixture; melting the mixture; agitating the molten mixture; allowing themixture to settle whereby duced to from l5to l0 The content of thecrucible was then allowed tosettle, for phase separation T1 1 .-';t;Whases, a thorium-containing magnesium-rich phase for about the same timeas rotation had been ca iedout and: ,uranium-rich phase are formed; andseparating said and then either quenchedbr permitted tofurna ce-cool;two phases.

i The preferred magnesium content is about 58 percent,

' because then the magnesium-thorium eutectic is formed ing the mixtureto about 1150 C. when both phases are I in the liquid state and theuranium-rich phase settles at the bottom, then cooling to below 585 C.,preferably to room temperature, whereby the uranium-rich phase and themagnesium-thorium alloy solidify and finally separating the uranium fromthe alloy by mechanical means. Under these conditions the uranium-richphase is obtained in one solid piece.

Or else, and this is the preferred method, the separation is carried outin two stages, namely, a preseparation and a final separation.Preseparation is effected by maintaining the reaction mass at atemperature above the melting point of the magnesium-thorium alloy butbelow the melting point of uranium, suitably just about above 585 C. inthe case of the magnesium-thorium eutectic, and decanting the bulk ofthe liquid magnesium-thorium alloy away from a residue comprising the'solid'uranium-rich particles and the remainder of the magnesium-thoriumalloy; recovery of the uraniumfrom the residue is then carried outaccording to the methods given below. In the case of using apreseparation step less uranium is lost with the magnesium-thorium alloyon account of the lower temperature-used and the lower uraniumsolubility at lower temperatures.-

The residue, according to this invention, can be processed by twomethods. One method comprises cooling of the residue to below themelting point of the magnesium-thorium alloy preferably to roomtemperature for solidification and separation of the solid uraniumrichphase from the solid remainder of magnesiumthoriurn alloy by mechanicalmeans. According to the 4 other method, the residue which then has atemperature of about 585 C. is heated to above the melting point ofuranium, which is about 1132 C., preferably to about 1150 C., wherebythe heavy liquid uranium-rich phase, which contains less than onepercent of thorium, separates and settles at the bottom of thecontainer; the masses are then cooled to room temperature. In this casethe use of the high temperature for melting the uranium does not involvea considerable uranium loss because the bulk of the magnesium-thoriumalloy has been removed so that there is very little of themagnesiumthorium alloy left for dissolving uranium. The solid onepieceuranium phase is then separated from the solid onepiecemagnesium-thorium alloy by mechanical means.

If chromium is added, it is preferably incorporated to the residue, thatis, after the bulk of the magnesiumthorium alloy has been removed bydecanting. The quantity of chromium is preferably 5.2 percent by Weightbased on the total amount of uranium present. The mass is then heatedtoa temperature within the range from 860 to 900 C., whereby theuranium-chromium eutectic settles at the bottom while themagnesium-thorium alloy collects above it. Cooling to room temperatureand separation by mechanical means complete the separation.

Separation by mechanical means can either be carried out by hitting themetallic mass with a hammer whereby the two solid pieces fall apart, orby removing the magnesium-thorium alloy by lathing; the latter ispreferred when there is very little magnesium-thorium alloy present withthe uranium-rich phase. For further cleaning the uranium piece can beimmersed in dilute nitric acid whereby any magnesiumrthorium alloy stilladhering to the surface is dissolved? The thorium content of the uraniumphase, which is always less than one percent, can then be reducedfurther by repeating the process with pure magnesium whereby the thoriumis dissolved in the magnesium but very little uranium is taken up.

Table II Mixing Settling Average chemical analyses Conditions ConditionsTypical charge grams I Time, Time, Mg-rlch U-rich mine. O. mine. O.phase, wt. phase, wt.

percent percent 1,000 00-120 800 {gSfiEg- 1,000 120-180 B800 {@fifi-S1,000 00-240 1.000 {@fgjfl:

1 000 Til-32.0.... 1:200 10 1,200 Th-1.2.

1.200 -10 1.200 Th32.0. 'Ih-0.85.

1,200 15 1,200 101-340-.-. Til-0.68.

1,000 10 1,200 Til-34.0-.-- Th-0.84.

1,200 10 1,200 Th-3.0..-- Hr-0.8.

'Ih-30 Til-0.4. 000 00-120 900 u-0.053 11-035.v

Or-0.13..... (Jr-5.6.

I Uranium shavin gs b Sample furnace-cooled from temperature indicated.

Aro-melte dell y. Y a Sample quenched instead or Iumace-cooled, fromtemperature indicated.

In view of the high reactivity of the metals involved, it is advisableto carry out the separation process under the exclusion of air; this isbest accomplished by operating in an inert atmosphere of helium or argongas.

The magnesium-rich phase can be processed by distillation for theseparation of the magnesium from the thorium.

A number of uranium-thorium separations were carried out using atechnique similar to that employed for the determination of thesolubilities and described above. The conditions and resultstogetherwith the compositions of the mixtures melted are compiled inTable II.

The balance of the magnesium-rich phase in each of the above exampleswas magnesium and that of the uranium-rich phase uranium. Theexperiments show that a good separation is accomplished by the processof this invention.

It will be understood that this invention is not to be limited to thedetails given herein, but that it may be modified within the scope ofthe appended claims.

What is claimed is: v I

1. A process of recovering uranium from metallic uranium-thoriummixtures, comprising adding magnesium to the mass in a quantity toobtain a content of from 48 to 85 percent by weight; melting and forminga magnesium-thorium alloy at a temperature of between 585 and 800 C.;agitating the mixture; allowing the mixture to settle whereby twophases, a thorium-containing magnesium-rich liquid phase and a soliduraniumrich phase are formed; and separating said two phases.

2. The'process of claim 1 wherein the phases are separated by heating toabout 1150 C. whereby both phases are melted and the uranium-rich phasesettles at the bottom, "then cooling both phases to room temperature forsolidification, and separating the uranium-rich phase from themagnesium-thorium phase by mechanical means.

3. The process of claim 1 wherein a phase preseparation is first carriedout by heating the phases to above the melting point of themagnesium-thorium alloy, but below the melting point of the uranium anddecanting the bulk of the magnesium-thorium alloy away from a residuecontaining the remainder of the magnesium-thorium alloy and solidparticles of the uranium-rich phase.

4. The process of claim 3 wherein magnesium is added in a quantity ofabout 58 percent and the preseparation temperature is about 585 C.

5. The process of claim 3 wherein said residue is cooled.

to room temperature whereby the uranium-rich phase and the remainder ofthe magnesium-thorium alloy solidify and the phase is separated from theremainder by mechanical means.

6. The process of claim 3 wherein said residue is heated to about 1150C. until the uranium-rich phase is melted and has settled at the bottom,it is then cooled to room temperature and the uranium-rich phase isseparated from said remainder of the alloy by mechanical means.

7. The process of claim 3 wherein from 5 to 5.2 percent of chromium,based on the quantity of uranium, is added to the residue, the mixturethus obtained is heated to from 860 to 900 C. until a liquid lightmagnesiumthorium alloy has separated from a liquid heavy uraniumchromiumeutectic, the alloy and the eutectic are then cooled to room temperatureand separated by mechanical means. V

8. The process of claim 1 wherein melting is carried out in an inertatmosphere.

9. The process of claim 1 wherein magnesium is added to the separateduranium-rich phase whereby a further decontamination from any thoriumstill present with the uranium is obtained.

10. A process of recovering uranium from metallic uranium-thoriummixtures, comprising adding magnesium in a quantity to obtain a contentof about 58 percent in the mixture and about 5.2 percent of chromiumbased on the uranium present in the mass; heating the mixture to about900 C. and agitating it for thorough contacting; allowing the mixture tosettle whereby two phases, a thorium-containing magnesium-rich phase anda uraniumchromium eutectic phase are formed; and separating said twophases.

References Cited in the file of this patent Lawroski: Survey ofSeparation Processes, P/ 823, 7

International Conference on the Peaceful Uses of Atomic Energy, v01. 9,pages 580-582 (1956). i

Finniston et al.: Metallurgy and Fuels, Progress in Nuclear Energy, vol.5, McGraw-Hill Book Co., N.Y. (1956), pages 169, 212, 253.

1. A PROCESS OF RECOVERING URANIUM FROM METALLIC URANIUM-THORIUMMIXTURES, COMPRISING ADDING MAGNESIUM TO THE MASS IN A QUANTITY TOOBTAIN A CONTENT OF FROM 48 TO 85 PERCENT BY WEIGHT, MELTING AND FORMINGA MAGNESIUM-THORIUM ALLOY AT A TEMPERATURE OF BETWEEN 585 AND 800*C.,AGITATING THE MIXTURE, ALLOWING THE MIXTURE TO SETTLE WHEREBY TWOPHASES, A THORIUM-CONTAINING MAGNESIUM-RICH LIQUID PHASE AND A SOLIDURANIUM-RICH PHASE ARE FORMED, AND SEPARATING SAID TWO PHASES.